From the prior art, such as DE 10 2010 045 037 A1, it is known how to interconnect a plurality of battery cells into a battery to provide a particular voltage or a particular current. Such batteries are used at present, in particular, as traction batteries in motor vehicles such as electric vehicles or hybrid vehicles for providing electrical drive energy.
An electrical voltage normally occurs at the connection terminals or battery poles of battery cells known from the prior art. By connecting in series a plurality of individual battery cells to form an overall system or battery, voltages of more than 60 volts are achieved in the manufacture of traction batteries, for example. Batteries with a voltage of more than 60 volts are also known as high-voltage batteries and they require corresponding protection measures.
In traction batteries for electric cars or hybrid vehicles, the electrical voltage at present is as much as 200 volts to 900 volts, and energy contents of up to 100 kilowatt-hours or more can be provided by such traction batteries. In particular, the construction of high-voltage batteries which can be used as traction batteries in motor vehicles such as electric vehicles or hybrid vehicles therefore requires the utmost precaution.
Already at voltages of more than 60 volts, appropriate protection measures must be taken for workers involved in the manufacture of the battery, such as the wearing of protective clothing, gloves, a helmet with visor, and the providing of coverings, and the like. Furthermore, an enormous expense is required in regard to the qualification and training in how to handle high-voltage batteries. Thus, at present there is a very large cost involved in making sure that no electrical dangers to persons are created when handling high-voltage batteries, especially during the manufacture of such a battery.
It is seen as being a drawback in this case that higher electrical voltages, such as voltages of >60 volts, may in the worst case be life-threatening. Furthermore, an enormous amount of energy may be released abruptly from high-voltage batteries. Electric arcs and short circuits may occur, injuring or killing people. Moreover, objects located near the battery may be damaged or involved in the accident.
It must be taken into account that electrical voltages cannot be recognized, detected, or felt in advance by the human senses. Only afterwards, for example, upon touching a component of a battery under voltage, is the presence of the electrical voltage recognized, but it is then already too late to avoid damage.
Measures for the safe construction and handling of high-voltage batteries are therefore very time-consuming and cost-intensive. Yet the danger of electric shock also exists for the persons who handle the battery after its manufacture, such as the customer service staff involved in the servicing of a battery. The same applies to a user of a motor vehicle outfitted with the battery. Moreover, first responders dealing with the battery after an accident with an electric vehicle or hybrid vehicle are also exposed to corresponding dangers from high-voltage batteries.
The manufacture of high-voltage batteries normally makes use of battery cells that are already active when the battery cell is delivered. Namely, as a rule, the battery cells are already precharged by the manufacturer, even though the state of charge is relatively low and may amount to around 10 percent to 15 percent of the maximum state of charge. Consequently, an electrical voltage is also already present at the two connection terminals or battery poles of the particular battery cell during the manufacture of the battery. Thus, when assembling high-voltage batteries one must expect more or less “live battery cells”. Even with the low state of charge, therefore, life-threatening high voltages may occur on account of the placement of the battery cells in a series connection.